The overall aim of these studies is to determine whether impaired serotonin function confers vulnerability to the aggression increasing effects of alcohol among women. More specifically, we propose to study the effects of alcohol and plasma L-tryptophan manipulations (and ultimately serotonin levels in the central nervous system) on aggressive responding in female subjects under controlled laboratory conditions. A naturalistic laboratory procedure will be used, which provides the participating subject with the opportunity to aggress toward a fictitious person who ostensibly presents an aversive stimulus to the subject. To identify the complete time-course effects of alcohol and/or the plasma L-tryptophan manipulations on behavior, subjects' responses will be evaluated at periodic intervals before and following drink administration. The effects of alcohol and amino-acid drink mixtures, which either increase (T+) or decrease (T-) plasma L- tryptophan levels, will be compared. Of particular importance will be the effects of these drink manipulations in two groups of women, who differ in the severity of menstrual related symptoms, at two different phases of the menstrual cycle. This is important because serotonin function appears to vary across the menstrual cycle phase (lower function during premenstrual phase) and is affected by the degree of premenstrual symptomatology experienced (lower function in women with high levels of symptomatology). These factors should differentially affect the efficacy of the drink administration (alcohol and/or amino-acid drinks). The specific aims of these laboratory studies are: l. To determine the differences in the effects of alcohol on aggression during the follicular and late- luteal (i.e., premenstrual) phases of the menstrual cycle; 2. To determine differences in the effects of the T+ and T- drinks on aggression during the follicular and late-luteal phases of the menstrual cycle; 3. To determine the interaction between alcohol combined with either the T+ or T- drinks on aggression; 4. To systematically examine how individuals with and without premenstrual symptomatology are differentially affected by the alcohol and L-tryptophan manipulation procedures; and 5. To determine how clinical instruments of aggression and impulsiveness are related to aggressive responding observed in the laboratory. These proposed studies will answer several questions regarding how alcohol, serotonin, premenstrual symptomatology, and the menstrual cycle are related to the susceptibility for aggressive behavior.